<?php
class MemberModel extends RelationModel {

    protected $_link = array(
        'MemberGroup'=>array(
            'mapping_type'   => BELONGS_TO,
            'class_name'     => 'MemberGroup',
            'foreign_key'    => 'groupid',
            'mapping_fields' => 'name',
            'as_fields'      => 'name:groupname',
        ),

    );

}